Mosses are small, non-vascular flowerless plants belonging to the taxonomic division Bryophyta sensu stricto. They typically grow in dense green clumps or mats, favoring damp and shady environments. While the term Bryophyta may also refer to the broader group of bryophytes—which includes liverworts and hornworts—mosses are a distinct category within this classification.
These plants generally stand between 0.2 and 10 cm tall, although some species reach greater heights; for example, Dawsonia superba is the world's tallest moss and can grow up to 60 cm. They lack seeds and instead develop sporophytes with unbranched stalks topped by capsules containing spores. Their structure consists of simple leaves, often only one cell thick, attached to stems that have limited capabilities for conducting water and nutrients.
There are approximately 12,000 species of mosses worldwide. Unlike vascular plants, their conducting tissues are poorly developed or structurally different from those found in more complex plant life.